Gengar Hex/Focus Blast as Blissey Attacker?
Gengar is resistant to Normal and Fairy. Focus Blast is super effective against Normal (even though there is no STAB), and Hex charges energy quickly and still pack a punch even with Blissey's resistance. Seems like he would be good for attacking/prestiging against Blissey, especially one without Psychic attacks.
Answers
Don't be so hasty. The difference between DG dealing 1.25x to everyone on your list and 0.8x to Gengar makes him 1.56x more tanky than his stamina number (120) would suggest. It's not quite that clear-cut due to the quick move varying in SE-normal-NVE on these pokes, but it's not as big a difference as you might think, since DG is a huge chunk of Blissey damage.
That moveset has 22 cycle DPS against Blissey (with perfect ATK IV Gengar, perfect DEF IV Blissey), which is pretty good. Plus, resisting Blissey's charge moves (and pound) goes a long way towards helping him survive. As a theorycraft, it's not going to beat Machamp, but if you evolved one I'd say it's pretty good to get the Blisseys low quickly. He may die, but he'll deal a lot of damage.
Edited edit: checked the other two Gengar movesets. H/ShadowB is worse (20.5), H/SludgeB is actually a bit better (22.3)
Sludge Bomb is the better one, because Blissey resists Ghost moves.
However, Gengar is not a very good attacker against Blissey. There are easy to get attackers with higher (edit:high) DPS and even slight type advantage, like:
Flareon: Fire Spin + Overheat
Charizard: Air Slash + Overheat
Alakazam: Psycho Cut or Confusion + Futuresight
Espeon: Confusion or ZH + Futuresight
Exeggutor: Extrasensory + Solar Beam
Edit: you are right PlentiCool, the DPS is not higher than Gengar, I meant that they perform better (because better STA and/or DEF (and ZH/DG Blissey)),
and should have written high instead of higher DPS
I honestly think Gengar will be fine and decent no matter if Blissey is SE with ZenH/Psychic.
Blissey can be a real timeout issue so you have to attack with something that can dish out a lot of damage minimum. If you get knocked out in the process, that's just part of the deal so attack with a Gengar, clean up with any of the others on the list or even a lowly Primeamp (which is more awesome now)...
Risking timeout is far worst IMO than getting knocked out and having to swap due to wasting 100 seconds of your time vs. 1 revive and potion.
Gengar also has lower max CP than Machamp so prestige gains should be better.
The key is you can't afford to timeout.
I've noticed for bulkier attackers, it probably is better just to absorb all the quick move hits to unleash the charge moves faster (like Solar Beam Exeggutors)...
